An eco-friendly vehicle may include a high voltage battery for supplying driving power, and an auxiliary battery for supplying power to electronic loads. Here, a low voltage DC-DC converter (LDC) connected to the auxiliary battery and the electronic loads may down-convert a voltage of the high voltage battery when a voltage of the auxiliary battery does not exceed a reference value under a control of an upper controller, thereby charging the auxiliary battery with the down-converted voltage.
In the LDC according to the related art, a gradient of a ramp signal used to generate a pulse width modulation (PWM) signal for controlling the LDC of the eco-friendly vehicle is unified. When a voltage reference is lower than a charging voltage of the auxiliary battery, the LDC may enter a current discontinuous mode in which current control response characteristics are slower. As a result, there are problems in that it may be impossible to perform a zero voltage switching (ZVS), which causes switching losses, an output ripple is deteriorated, and noise is caused in components of a type of core (e.g., a transformer, an inductor, etc.).